How Large Portion Sizes Can Hurt A Restaurant's Business

Twitter/@JohnTLibertyI'm not a big fan of milkshakes. But after a dental operation a few years ago, I decided to try one again. Not too bad, I remember thinking as I sipped the cool, chocolaty concoction. Unfortunately, a bad reaction to my pain medication later that evening meant the milkshake became associated with less than pleasant memories. I haven't had another since.

Memories can play an important role in how soon we want to eat a food again. A person's memory of the last few bites of a food appear to be especially influential, according to new research published in Psychological Science this month. In fact, the research suggests the memory of the last few bites of a large portion size may actually encourage people to eat a food less frequently. Understanding the factors affecting when people choose to eat is important, as companies profit from both the sale of individual items and how frequently those items are sold, according to lead author Emily Garbinsky.

One portion of the Psychological Science study involved researchers directing 134 Stanford University students to eat either a small or large portion of Nut Thin crackers and rate their enjoyment of each cracker after eating it. The next day, they were asked when they would like to receive a giveaway box of the crackers.

The students who ate the larger portion of crackers said they had less enjoyment at the end of the eating experience than students who ate the smaller portion of crackers. This result is likely due to a phenomenon called sensory-specific satiety, or the idea that consuming more of a food decreases how much a person enjoys that food during the current sitting.

While sensory-specific satiety has been shown to affect a person's consumption of a food in a specific sitting, the researchers' findings suggest it may also affect when they choose to consume the food again. In the study, participants who ate the smaller portion of Nut Thins and had higher end enjoyment chose to receive the giveaway box of Nut Thins sooner than the participants who ate the larger portion of Nut Thins and had lower end enjoyment.

The researchers think the finding may be due to a recency bias in memory, an effect that means the memory of the end of an eating experience is more influential than the memory of the beginning of the experience. With information from other experiments in the study, they concluded that the recency bias may be due to memory interference, which refers to a cognitive psychology theory that says new memories can interfere with old memories and vice versa.

While large portions are the norm for many restaurant meals and ready-to-eat foods, phenomena such as sensory-specific satiety and recency bias could mean consumers choose to eat these foods less frequently.

"Companies [currently] want to sell large portion sizes for lots of reasons," said Garbinsky, a doctoral candidate at the Stanford Graduate School of Business. "They can charge more, number one, and number two, consumers say they want large portions."

Much research remains to be done in this area, as the authors note. For example, consumers have more freedom to choose their portions than the subjects in the study. But if further research supports the translation of these findings to the field, companies might benefit from moving their super sizes to smaller sizes, a change that could promote consumer health as well.

About the Author: Julianne Wyrick has a bachelor's in biochemistry and is currently a master's student in the health and medical journalism program at the University of Georgia, where she also writes about science for the Office of Research Communications. Find her on the web at juliannewyrick.com. Follow on Twitter @juliannewyrick.